Thank you!
I tried it in safe mode (without switching anything else) and then my Forum looks like the Foundation theme and I still see some unexpected white areas:
I will try turning on and off some things, but if that triggers any ideas, please let me know!
UPDATE: When I switch to use Foundation (not in safe mode) as my preferred theme, I see white all over:
When I go back to Horizon and check the appropriate color palette, I don’t see any white:
I didn’t have this issue before so I’m guessing it might be one of the upcoming changes.